I think Melissa was trying to have one of those feel good "meet in the middle" moments with Marie by condemning the violence and when Newt started bringing up the obvious truth, she made her comment to make it so Marie wouldn't have to engage in an argument before they were up against a break. That's my take. If they were truly trying to muzzle Newt, they wouldn't have let him finish his thought IMO and it doesn't really fit with Harris' character especially.